-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 101310
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
810 AM EST TUE DEC 10 2013

.SYNOPSIS...
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A POTENT UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE REGION
TODAY. ARCTIC HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT THROUGH
THE END OF THE WEEK. LOW PRESSURE MAY IMPACT THE REGION THIS
WEEKEND.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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...UPDATE TO DOWNGRADE THE WINTER STORM WARNING TO AN ADVISORY FOR
THE CENTRAL SHENANDOAH VALLEY INTO CENTRAL VIRGINIA.
ELSEWHERE...THE WINTER WEATHER HEADLINES HAVE NOT CHANGED. THE
HEAVIEST IS EXPECTED TO BE NEAR AND EAST OF THE BLUE RIDGE
MOUNTAINS DURING THE MID TO LATE MORNING HOURS. THE PREVIOUS
DISCUSSION FOLLOWS...


LTST SFC ANALY DEPICT LOPRES IN WRN VA/NC. LOW A SFC REFLECTION OF
VORTMAX/RRQ OF 180 KT UPR JET. ASSOCD PCPN HAS RAPIDLY BEEN FILLING
IN ACRS THE OH/TN VLYS...AND IS ON THE WRN DOORSTEP ATTM. GDNC IN
GOOD AGREEMENT THAT THIS WL BE TRACKING ACRS CWFA...PRIMARILY BTWN
12-18 UTC.

THE ARRIVAL OF THIS PCPN WL PROVIDE ENUF MIXING TO ERODE FOG
CURRENTLY IN PLACE. A STRIP OF DENSE FOG RESIDES FM CHO-IAD. TRENDS
SINCE 04Z INDICATE A SLOW IMPRVMNT HAS BEGUN...AND HV ALLWD DENSE
FOG ADVY TO EXPIRE AT 08Z. AFTER THAT...VSBY STILL WONT BE
GREAT...AS FOG RESTRICTIONS WL BE REPLACED W/ SNOW RESTRICTIONS.

THE FEATURES RESPONSIBLE FOR THE SNOW LOOK TO BE PROGRESSIVE.
BUT...LIFT VIGOROUS AND H7-5 F-VECTORS DO POINT TO MESOSCALE
BANDING. WHILE MAX LIFT NOT EXACTLY IN DENTRITIC GROWTH ZONE...A
THIRD TO HALF INCH LIQ QPF SUGGESTS THAT WRNG CRITERIA THREATENED.
CANNOT PLACE EXACTLY WHERE THE BANDS WL SET UP /LTST HRRR AND WRF
RUNS SUGGEST CHO-DCA-MTN/...FEEL FAIRLY CONFIDENT THAT LCLLY HIER
AMTS PSBL. GFS SUGGESTS THAT THE BAND MAY BE NW OF CURRENT 3-6
INCH FCST STRIPE. CONFIDENCE DIMINISHES TWD EZF AND SRN MD DUE TO
LOWER SNW RATIOS AND MDL SNDGS SUGGESTING PL WL MIX IN. BOTH OF
THESE FACTORS WL REDUCE SNW TTLS.

IN LIGHT OF 00Z GDNC...POTL FOR HIER TTLS...AND NOT CERTAIN BANDS
WL BE W/IN PREVIOUS WRNG AREA...HV OPTED TO WIDEN WRNG AREA TO INCL
LUA-FDK ON THE NW AND CHO- OMH ON THE SE. TIME FRAME NOT EXTENDED
AS GDNC STILL PRETTY INSISTENT THAT SNOW SHUD BE ENDING BY 18Z.
MAY EVEN SEE BRIGHTENING SKIES BEFORE SUNSET. ONCE SNOW
STARTS...TEMPS CHGG LTL...AND FCST MAXT REFLECTS THAT.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
HIPRES BLDS TNGT...WL BE ARND THRU WED NGT. SUBSIDENCE INCREASES
RAPIDLY...PROVIDING ONLY A SMALL WINDOW FOR UPSLP SHSN THIS EVNG.
OTRW...MOCLR SKIES AND CAA DOMINATE THE PD. TOOK MOS BLEND FOR
TEMPS.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A LONG WAVE TROUGH SHOULD MOVE OFF THE EAST COAST FRIDAY AS HIGH
PRESSURE MOVES TO OUR SOUTH. A SLIGHT RELIEF IN TEMPERATURES IS
EXPECTED SATURDAY AS RETURN FLOW BRINGS TEMPS IN THE 40S INTO THE
REGION. A COLORADO LOW IS EXPECTED TO FORM MID WEEK AND TRAVEL CLOSE
TO THE GULF STATES BEFORE MAKING A TURN UP THE TN VALLEY AND TOWARDS
THE MID ATLANTIC. BOTH THE GFS AND ECMWF ARE ON BOARD WITH THIS
TREND AND A WINTRY MIX IS EXPECTED AS IT APPROACHES THE MID
ATLANTIC. PTYPE AND TIMING SPECIFICS ARE STILL IN QUESTION. LOW
PRESSURE MOVES TOWARDS NEW ENGLAND SUNDAY AND BREEZY COOLER
CONDITIONS ARE EXPECTED FOR THE MID ATLANTIC.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
LIFR STILL WIDESPREAD...BUT FOG SHUD BE LIFTING BEFORE DAWN.
HWVR...VSBY RESTRICTIONS DUE TO FOG WL BE REPLACED BY RESTRICTIONS
DUE TO SNOW. ONSET PRIOR TO 12Z. POOR CONDS WL CONT THRU 18Z.

VFR TNGT-FRI UNDER HIPRES. DIMINISHED CIGS/VSBYS PSBL SAT AHD OF
THE NEXT SYSTEM TO IMPACT THE RGN.

&&

.MARINE...
WNDS BLO 10 KT ATTM. MIXING REMAINS POOR THRU THE DAY. HWVR...AS A
DISTURBANCE GLIDES BY...PROVIDING A PD OF SNOW...PERHAPS MIXED W/ PL
AND A LTL RA IN THE MID BAY...SOME GDNC SUGGESTING WNDS WL PICK UP.
HV NOT FLLWD THAT SOLN ATTM...AND HV CAPPED WNDS AT 15 KT. WL NEED
TO MONITOR IN CASE A SCA REQD.

IN THE WAKE OF THE LOW...COLD AIR WL STREAM IN...PROVIDING A SETUP
FOR MORE FVRBL MIXING. WL KEEP SCA IN PLACE TNGT. WNDS DIMINISH FOR
WED UNDER HIPRES...WHICH WL BE ARND THRU FRI. A DISTURBANCE MOVE
INTO OVR THE WATERS SAT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER STORM WARNING UNTIL 2 PM EST THIS AFTERNOON FOR DCZ001.
MD...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR
     MDZ003-016>018-501-502.
     WINTER STORM WARNING UNTIL 2 PM EST THIS AFTERNOON FOR
     MDZ004>007-009>011-013-014.
VA...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR
     VAZ025-026-028-036>038-050-055>057-503-504.
     WINTER STORM WARNING UNTIL 2 PM EST THIS AFTERNOON FOR VAZ027-
     029>031-039-040-042-051>054-501-502.
WV...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR
     WVZ050>053-055-501>506.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     WEDNESDAY FOR ANZ530>543.
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&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS/BJL
SHORT TERM...HTS
LONG TERM...HAS
AVIATION...HTS
MARINE...HTS